Evaluating the impact of antiretroviral and antiseizure medication interactions on treatment effectiveness among outpatient clinic attendees with HIV in Zambia

OBJECTIVE: Interactions between enzyme-inducing anti-seizure medications (EI-ASMs) and antiretroviral drugs (ARVs) can lead to decreased ARV levels and may increase the likelihood of viral resistance. We conducted a study to determine if co-usage of ARVs and EI-ASMs is associated with ARV-resistant HIV among people living with HIV in Zambia. METHODS: Eligible participants were ≥18 years of age, concurrently taking ASMs and ARVs for at least 1 month of the prior 6-month period. Data was obtained regarding medication and HIV history. CD4 counts, plasma viral loads (pVL), and HIV genotype and resistance profile in participants with a pVL> 1000 copies/ml were obtained. Pearson’s test of independence was used to determine whether treatment with EI-ASM was associated with pVL>1000/mL copies. RESULTS: Of 50 participants, 41 (82%) were on carbamazepine (37 on monotherapy), all had stable regimens in the prior 6 months. Among the 13 ARV regimens used, 68% had a TDF/3TC backbone. The majority (94%) were on a stable ARV regimen for > 6 months. Median CD4 nadir was 205 (IQR 88–389) cells/mm3, and 60% of participants had commenced ARVs treatment before advanced disease occurred. Mean CD4 count at enrollment was 464 cells/mm(3) (SD 226.3). Seven participants (14%) had a CD4 count1000 copies/mL, all were on carbamazepine. Three participants with elevated pVL had a CD4 count < 200 cells/mm(3). None had documented adherence concerns by providers; however, 2 had events concerning for clinical failure. HIV genotype testing showed mutations in 3 participants. Carbamazepine was not found to correlate with elevated pVL (p=0.58). SIGNIFICANCE: EI-ASMs are commonly used in sub-Saharan Africa. Despite concurrent use of EI-ASMs and ARVs, the majority of participants showed CD4 counts > 200 cells/mm3 and were virally suppressed. Carbamazepine was not associated with an increased risk of virological failure or ARV-resistant HIV.